The following are known results which are also valid for the confluent cases of the Heun equation [1]}.
The three-term recurrence relations for the coefficients \(b_n\) 
of one-sided solutions
have the form
\(\alpha _{0}b_{1}+\beta _{0}b_{0}=0,\qquad \alpha _{n}b_{n+1}+\beta _{n}b_{n}+\gamma _{n}b_{n-1}=0\qquad (n\ge 1),\) 
